1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display device for maintaining a picture quality in a divisional driving mode for a large-scale/high-resolution liquid crystal display panel.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) controls light transmittance of liquid crystal cells arranged in a matrix pattern in response to video signals, thereby displaying a picture corresponding to the video signals on the liquid crystal display panel.
To this end, the LCD includes an active area having liquid crystal cells arranged in an active matrix type and driving circuits for driving the liquid crystal cells at the active area. More specifically, the LCD includes upper and lower plates. A plurality of thin film transistors (TFT's) for switching the liquid crystal cells, driving circuits for driving the thin film transistors and signal lines connected between the driving circuits and the TFT's are mounted on the lower substrate. The upper plate is provided with color filters separated for each cell area by black matrix stripes in correspondence with the matrix liquid crystal cells and transparent electrodes coated on the color filters, and spacers provided between the upper and lower plates to maintain a constant cell gap. A liquid crystal is filled in a space defined between the upper and lower plates by the spacers.
Such an LCD is fabricated by separately preparing the upper plate and the lower plate. After the two plates are attached to each other, a liquid crystal is injected between the plates through a liquid crystal injection hole. Thereafter, the LCD is completed by coating the liquid crystal injection hole with a sealant and curing the sealant.
The driving circuits require a plurality of driving integrated circuits (D-IC) connected to a plurality of data lines and gate lines to apply data signals and a scanning signal to the data lines and the gate lines, respectively. As the LCD is capable of realizing a large scale and a high resolution, a display speed of the liquid crystal display panel becomes slow because the time required for allowing the D-IC to conduct all the TFT's is extended. For this reason, when a gate voltage level is set to be too high, a voltage drop occurs from a pixel due to a feed through phenomenon, upon turning off the gate voltage, thereby causing a more serious distortion in picture quality.
Accordingly, there is a demand for a divisional driving of the liquid crystal display panel to overcome the problem as discussed above.
In such a divisional driving method for the liquid crystal display panel, as shown in FIG. 1, each data lines of the panel is physically cut at the half point “A” in FIG. 1.
In FIG. 1, the conventional LCD includes TFT's provided at the intersections between a plurality of gate lines 7 and 9 and data lines 3 and 5, upper and lower source drive IC's (SD-IC) 2 and 4 for applying data signals to the data lines 3 and 5 physically divided into the upper side and the lower side. Left and right gate drive IC's (GD-IC) 6 and 8 applies scanning signals to the upper and lower gate lines 7 and 9 that are divided only based on a signal without a physical division.
The upper SD-IC 2 applies the data signals to the data lines 3 of the first divided panel positioned at the upper portion of the panel in which the data lines 3 and 5 are cut at the half point “A” of the panel. The lower SD-IC 4 applies the data signals to the data lines 5 of the second divided panel positioned at the lower portion of the panel in which the data lines 3 and 5 are cut at the half point “A” of the panel.
The left GD-IC 6 and the right GD-IC 8 apply scanning signal to the upper and lower gate lines 7 and 9 to turn on the TFT'S.
In the LCD, in order to display a picture on each pixel, data signals are applied from the upper and lower SD-IC 2 and 4 to the data lines 3 and 5. Scanning signals from the left and right GD-IC 6 and 8 are sequentially applied to the gate lines 7 and 9 crossing the data lines 3 and 5 to turn on the TFT's. Accordingly, the data signal is applied through source and drain electrodes of the TFT to the pixel electrode, thereby displaying a picture on each pixel.
The upper and lower data lines 3 and 5 are driven independently as shown in FIG. 2. Thus, upon implementing the images, a difference in the picture quality is caused between the first divided panel and the second divided panel. More specifically, the TFT's on the panel improve a sustaining characteristic of the data signals applied to the pixels with the aid of storage capacitors (not shown). Also, the TFT's stabilize a gray scale display and maintain pixel information while the pixels are in a non-selection interval.
The storage capacitors connected to the pixels of the first divided panel are connected to the pre-stage gate lines to charge applied voltages. On the other hand, the storage capacitors connected to the first pixels of the second divided panel cannot charge voltages from the pre-stage gate lines at the non-selection interval because no pre-stage gate line at the storage capacitors is caused by the vertical division. As a result, there is a difference in a picture quality between the first divided panel and the second divided panel.
Moreover, the conventional LCD has an additional problem in that a circuitry configuration becomes complicated since a frame memory should be used as a panel driving apparatus for a divisional driving.